(1) Technical Field
The present document relates to DC-to-DC converters or amplifiers. In particular, the present document relates to a method and system for biasing internal nodes from reservoir capacitor during power down rather from battery.
(2) Background
In existing designs the output of a low drop-out (LDO) regulator or amplifier or buffer is pulled down and an output capacitor is discharged actively when the system as e.g. an LDO is powered down.
If the system as e.g. an LDO is frequently enabled and disabled a lot of power would be wasted in charging and actively discharging an external reservoir capacitor.
Even if the pull down was disabled to save power a clean startup cannot be guaranteed under all operating conditions. It would always depend on the discharged value of the output capacitor. The startup time specification would be violated along with overshoot and under shoot at the output.
This leads to following disadvantages                1. Increased power consumption in pulsed enabling of LDO or other systems        2. No guaranteed clean start-up process        3. Power consumption from battery or other supply required to bias the internal nodes under power down condition        
It is a challenge for engineers to design biasing of internal nodes, enabling a clean start-up process while minimizing power consumption.